New Zealand Journal of Marine and Freshwater Research abstracts

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Chemical processes affecting trace metal transport in the Waihou River and estuary, New Zealand

JENNY G. WEBSTER

Institute of Environmental Science &
Research Ltd
Private Bag 92-021
Auckland, New Zealand

Abstract  The Waihou River, North Island, New Zealand, receives trace metals from two contaminated drainage systems: Ohinemuri River and Tui Stream. In the upper Waihou River and its tributaries, trace metals are transported in bed sediments and in the water column--the latter providing a low-level but continuous flux of dissolved metals (particularly Cu, Zn, Mn, and As) and/or metals bound to suspended sediments (particularly As, Fe, and Pb). As the river water becomes saline, suspended sediment flocculates and settles, increasing the trace metal concentration of estuarine sediments relative to those of the upper river. Fe, Mn, Pb, and Zn are fully adsorbed onto the suspended sediment in the estuary, and should be effectively removed from the water column by this process. Cu and As are only partially adsorbed and are unlikely to be completely removed from the water column in the estuary region. Trace metal partitioning between dissolved and particulate phases appears to be generally consistent with regulation by adsorption onto hydrous iron-oxide in the sediments.

Keywords  Waihou River; trace metals; transport; iron-oxide

New Zealand Journal of Marine and Freshwater Research, 1995: Vol. 29: 539-553

0028-8330/95/2904-0539 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (995K); (scanned from paper original: notes about this process)

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